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Flagg Park pedestrian bridge reinstalled east of Lafayette

11-ton bridge over Coal Creek was taken out and washed downstream during September's flood

By Doug Pike

Colorado Hometown Weekly

Posted:
11/07/2013 12:26:14 PM MST

Updated:
11/07/2013 12:30:53 PM MST

A crane truck drops a pedestrian bridge back into place Wednesday, Nov. 6, across Coal Creek near Flagg Park east of Lafayette. The bridge was dislodged and swept downstream during the September floods. (Doug Pike / Colorado Hometown Weekly)

The pedestrian bridge over Coal Creek at Flagg Park east of Lafayette was unearthed and repositioned Wednesday, Nov. 6, nearly two months after it gave way to flood waters.

The 22,000-pound structure was no match for the torrents of Coal Creek during the September flood, breaking free from its abutments and drifting downstream.

Work crews spent Wednesday morning clearing mud and debris from the bridge, which for the past eight weeks resided at the bottom of the creek bed. Fortunately, due a design that accounts for flooding, the bridge survived the ordeal structurally intact.

"Our ultimate goal today was to just pick up the bridge and put it up on blocks so it could be inspected," said Jesse Coffman of Pro Lift Crane Service, which extracted the bridge. "The flood transposed it about 150 feet downstream."

Brent Wheeler, a project engineer with Boulder County Parks and Open Space, said structural engineers looked over the bridge and found no cracks, no breaks in the welds and no deformities. Engineers declared it fit for reinstallation.

The bridge is designed to sit on reinforced mounting pegs on each end but isn't bolted down. In the event that flooding lifts it off its mounts, the structure, which is tethered by a cable on one end, is designed to pivot to reposition itself lengthwise in the direction of the water flow.

In this case, it appears the design worked.

"The design allowed the water to flow instead of forcing the bridge to act like a dam," Coffman said. "It just looked like it had some cosmetic damage from all the rocks that hit it while it was down in the creek bottom. But that's it."

The concrete bridge abutments, which saw significant washout around their bases, didn't sustain any damage either.

"We're pretty pleased," Wheeler said. "We got it all done in one operation. They dropped it back in place and it still fit."

Urban Drainage was tapped by Boulder County to conduct and subcontract out the work.

"They're better suited for a lot of this than we are," Wheeler said. "Parks and Open Space focuses more on trails and trail repairs."

While much of the Coal Creek Trail remains closed due to flood damage, the section of the trail system that the Flagg Park bridge provides access to was reopened a couple weeks ago, Wheeler said. Flagg Park and the bridge remain closed.

The Coal Creek/Rock Creek Trail system is open between Colorado Highway 7 and Exempla Good Samaritan Medical Center. The trail is closed north of Hwy. 7 and south of Exempla.

The Flagg Park parking area is slated for improvements which will transform it into a regional trailhead, Wheeler said. The county hopes to begin that project early next year.

A work crew works Wednesday, Nov. 6, to position a bridge over Coal Creek near Flagg Park, east of Lafayette. (Doug Pike / Colorado Hometown Weekly)

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